1. Field of the Invention
This invention relates to a novel bilirubin oxidase and to a process for its production. More specifically, this invention relates to novel thermostable bilirubin oxidase and a process for the production of bilirubin oxidase which comprises culturing a bilirubin oxidase producing microorganism belonging to the genus Bacillus and then preparing the resultant bilirubin oxidase from the cultured broth.
2. Discussion of the Background
Bilirubin oxidase has conventionally been known as an enzyme which has substrate specificity to bilirubin and catalyzes a reaction in which biliverdin and water are formed from bilirubin and oxygen. As microorganisms capable of producing bilirubin oxidase, have been reported certain Myrothecium genus [N. Tanaka and S. Murao, Agric. Biol. Chem., 46, 2499 (1982)], Schizophyllum genus (Japanese Patent Laid-Open No. 135886/1984), and Coprinus, Trametes, Lenzites, Coriolus, Pholiota, Pleurotus and Fomitopsis genus (Japanese Patent Laid-Open No. 198971/1984).
Bilirubin oxidase has been attracting interests in recent years as a reagent for determining of bilirubin content and removing bilirubin which causes errors to analysis of other biochemical substance(s) in serum samples in the field of clinical chemistry. Among conventional bilirubin oxidase samples, the Myrothecium-originated enzyme is stable for 15 minutes as 37.degree. C. but its residual activity is as little as 20% or so at 70.degree. C. On the other hand, the Schizophyllum-originated enzyme is stable for 10 minutes up to 45.degree. C. only. The enzyme samples originated from other producing microorganisms, for example, the Coprinus-originated enzyme exhibits residual activity of 90-95% after held for 10 minutes at 60.degree. C. and is not satisfactory in thermal stability. They thus require strict temperature control during their production and treatments. When they are immobilized as one way of their application, they may be deactivated depending on conditions for their immobilization. They are hence not fully satisfactory in their handling readiness.